The invention relates to a sample vessel for NMR measurements, comprising a vessel material of magnetic susceptibility χ2,
with an outer interface that delimits the sample vessel with respect to the environment,
and with an inner interface that delimits the sample vessel with respect to the sample volume, wherein the outer interface comprises
                an outer cylindrical surface that is a cylinder envelope whose axis of symmetry is aligned parallel with a z-direction,        and an outer closing surface that closes the bottom of the sample vessel and is joined to the outer cylindrical surface,wherein the inner interface comprises        an inner cylindrical surface that is a cylinder envelope whose axis of symmetry is aligned parallel with the z-direction,        and an inner closing surface that closes the sample volume at the lower end and is joined to the inner cylindrical surface.        
Such a sample vessel has become known through SCHOTT Duran Laboratory Glassware Catalog 2005/2006, p. 62.
NMR spectroscopy is a method of instrumental analysis with which a measurement sample is exposed to a strong static magnetic field. The measurement sample is then exposed to electromagnetic pulses and the reaction of the atomic nuclei in the measurement sample is measured and analyzed.
One prerequisite for high-quality measurement results is good homogeneity of the static magnetic field in the measurement sample. The measurement sample (usually a substance dissolved in a solvent such as acetone or water, that is, a liquid sample) is held in a sample vessel. Inside, the sample vessel generally distorts the magnetic field that is homogeneous and static outside, potentially resulting in measurement results of poorer quality.
In the case of standard sample vessels, such as are familiar from the SCHOTT Duran Glassware Catalog, the sample vessel has a section shaped as a cylinder envelope and a bowl-shaped section closing the end; the wall thickness is essentially constant throughout. Whereas the section having the shape of a cylinder envelope causes only minor distortions, the closing section can produce strong field distortions. Distortion of the magnetic field is avoided by using only a small portion of the sample volume as the measured volume (sample volume=region of the sample vessel filled with measurement sample) and at a sufficient distance from the closing section. Thus, only a small part of the available mass of the sample is actually measured, which results in a poorer signal-to-noise ratio. This is particularly significant if only a small quantity of the sample substance is available and it has to be diluted to fill the entire sample volume.
Further, sample vessels are already known, wherein the space between the lower end of the sample vessel and the measured region is solid, avoiding the need to fill this space with the substance to be measured. However, in this case, the inner interface between the sample vessel and the measurement sample (usually a liquid sample) can cause magnetic field distortions in the sample volume. From [2], it is known that the magnetic susceptibility of the material of the sample vessel may be chosen in accordance with the magnetic susceptibility of the liquid sample in order to reduce distortions [2]. However, it is difficult and expensive to adjust the susceptibility of the material of the sample vessel. It is also known that the inner interface of the sample vessel may be shaped as a spheroid, for example, by having a spherical shape [4] or by insertion of shaping inserts [5], which also reduces distortions.
In all these sample vessels, the lower end of the sample vessel must be far from the measured region, such as the interior of an RF resonator system, to avoid distortions of the static magnetic field in the measured region. Consequently, it is necessary to leave enough space in the measurement probe below the measured region for the lower end of the sample vessel.
By contrast, the objective of this invention is to present a sample vessel in whose sample volume a high homogeneity of the static magnetic field can be achieved essentially everywhere, permitting a more compact measurement probe.